Oscillator, electronic apparatus, and vehicle

ABSTRACT

An oscillator includes a resonator, a temperature control element that controls a temperature of the resonator, a first temperature sensing element that outputs a first temperature detection signal, a second temperature sensing element that is provided at a position farther from the resonator than the first temperature sensing element and outputs a second temperature detection signal, an analog/digital conversion circuit that converts the first temperature detection signal into a first temperature code which is a digital signal, and converts the second temperature detection signal into a second temperature code which is a digital signal, and a digital signal processing circuit that generates a temperature control code for controlling the temperature control element based on the first temperature code and the second temperature code.

The present application is based on, and claims priority from JPApplication Serial Number 2019-057886, filed Mar. 26, 2019, thedisclosure of which is hereby incorporated by reference herein in itsentirety.

BACKGROUND 1. Technical Field

The present disclosure relates to an oscillator, an electronicapparatus, and a vehicle.

2. Related Art

In JP-A-2014-197751, an oven controlled crystal oscillator (OCXO)including a heating element that heats a resonator, a temperaturecontrol circuit that controls the heating element based on a detectionsignal of a thermistor, and a temperature compensation circuit thatcorrects a primary component and a secondary component offrequency-temperature characteristics of an oscillation signal based ona detected value of a temperature sensor is described. According to theoven controlled crystal oscillator, it is possible to estimate atemperature change of the resonator by capturing a change in outside airtemperature of the oscillator by the temperature sensor, and to correcta frequency of the oscillation signal.

However, in the oven controlled crystal oscillator described inJP-A-2014-197751, since temperature control is performed based only onthe detection signal of the thermistor, it is difficult to achieve bothhighly sensitive detection of fluctuation in the outside air temperatureand accurate detection of the temperature of the resonator. For thatreason, accuracy of temperature control may be reduced.

SUMMARY

An oscillator according to an aspect of the present disclosure includesa resonator, a temperature control element that controls a temperatureof the resonator, a first temperature sensing element that outputs afirst temperature detection signal, a second temperature sensing elementthat is provided at a position farther from the resonator than the firsttemperature sensing element and outputs a second temperature detectionsignal, an analog/digital conversion circuit that converts the firsttemperature detection signal into a first temperature code which is adigital signal, and converts the second temperature detection signalinto a second temperature code which is a digital signal, and a digitalsignal processing circuit that generates a temperature control code forcontrolling the temperature control element based on the firsttemperature code and the second temperature code.

In the oscillator according to the aspect, the digital signal processingcircuit may generate a first correction code based on the secondtemperature code and generate the temperature control code based on acode obtained by adding the first correction code to the firsttemperature code.

In the oscillator according to the aspect, the analog/digital conversioncircuit may convert a power supply voltage into a power supply voltagecode which is a digital signal, and the digital signal processingcircuit may generate the temperature control code based on the firsttemperature code, the second temperature code, and the power supplyvoltage code.

In the oscillator according to the aspect, the digital signal processingcircuit may generate a second correction code based on the power supplyvoltage code, and generate the temperature control code based on a codeobtained by adding the second correction code to the first temperaturecode.

In the oscillator according to the aspect, the digital signal processingcircuit may generate the second correction code based on a high-orderexpression of a third or higher order using the power supply voltagecode as a variable.

In the oscillator according to the aspect, the digital signal processingcircuit may perform a control operation based on the first temperaturecode and the second temperature code, and generate the temperaturecontrol code based on a code obtained by the control operation.

In the oscillator according to the aspect, the control operation mayinclude a proportional operation and an integral operation.

In the oscillator according to the aspect, the digital signal processingcircuit may generate the temperature control code by performingdelta-sigma modulation a code obtained based on the control operation.

In the oscillator according to the aspect, the digital signal processingcircuit may integrate the code obtained based on the control operationat a rate faster than an update rate of the first temperature code, andoutput a carry bit of the integrated code as the temperature controlcode.

In the oscillator according to the aspect, an analog filter to which thetemperature control code is input may be further included, and thetemperature control element may be controlled based on a signal outputfrom the analog filter.

In the oscillator according to the aspect, an integrated circuit elementthat includes the digital signal processing circuit and the secondtemperature sensing element may be further included.

An electronic apparatus according to another aspect of the presentdisclosure includes the oscillator according to the aspect and aprocessing circuit that operates based on an output signal from theoscillator.

A vehicle according to another aspect of the present disclosure includesthe oscillator according to the aspect and a processing circuit thatoperates based on an output signal from the oscillator.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an oscillator according to anembodiment of the present disclosure.

FIG. 2 is a plan view of the oscillator according to the embodiment ofthe present disclosure.

FIG. 3 is a cross-sectional view illustrating a resonator and leadterminals.

FIG. 4 is a bottom view illustrating the resonator and the leadterminals.

FIG. 5 is a functional block diagram of an oscillator according to afirst embodiment.

FIG. 6 is a graph illustrating an example of a relationship between anoutside air temperature, a temperature of a resonator, and a temperatureof an integrated circuit element in an oven controlled crystaloscillator according to a comparative example.

FIG. 7 is a diagram illustrating an example of temperature control codegeneration processing by a digital signal processing circuit in thefirst embodiment.

FIG. 8 is a graph illustrating an example of waveforms of thetemperature control code and a temperature control signal.

FIG. 9 is a graph illustrating an example of a relationship between apower supply voltage and the temperature of the integrated circuitelement.

FIG. 10 is a graph illustrating an example of a relationship between thepower supply voltage and the temperature of the resonator.

FIG. 11 is a functional block diagram of an oscillator of a secondembodiment.

FIG. 12 is a diagram illustrating an example of temperature control codegeneration processing by a digital signal processing circuit in thesecond embodiment.

FIG. 13 is a cross-sectional view of an oscillator according to amodification example.

FIG. 14 is a functional block diagram of an electronic apparatusaccording to the embodiment of the present disclosure.

FIG. 15 is a diagram illustrating an example of an appearance of theelectronic apparatus according to the embodiment of the presentdisclosure.

FIG. 16 is a diagram illustrating an example of a vehicle according tothe embodiment of the present disclosure.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, exemplary embodiments of the present disclosure will bedescribed in detail with reference to the drawings. The embodimentsdescribed below do not unduly limit contents of the present disclosuredescribed in the appended claims. Also, not all of the configurationsdescribed below are essential constituent requirements of the presentdisclosure.

1. Oscillator 1-1. First Embodiment 1-1-1. Oscillator Structure

FIGS. 1 and 2 are diagrams illustrating an example of a structure of anoscillator 1 according to the first embodiment. FIG. 1 is across-sectional view of the oscillator 1, and FIG. 2 is a plan view ofthe oscillator 1. In FIG. 2, a cap is seen through for convenience ofexplanation. FIG. 3 is a cross-sectional view illustrating a resonatorand lead terminals accommodated in the oscillator, and FIG. 4 is abottom view illustrating the resonator and the lead terminals.

In FIG. 1 to FIG. 4, for convenience of explanation, three axes that areorthogonal to each other are set as an X-axis, a Y-axis, and a Z-axis,and the Z-axis coincides with the thickness direction of the oscillator,in other words, an arrangement direction of a base and a cap bonded tothe base. The X-axis is along a direction in which the lead terminalsarranged in two rows face each other, and the Y-axis is along anarrangement direction of the lead terminals. A direction parallel to theX-axis may be referred to as “X-axis direction”, a direction parallel tothe Y-axis may be referred to as “Y-axis direction”, and a directionparallel to the Z-axis may be referred to as “Z-axis direction”. InFIGS. 1 to 4, illustration of wiring patterns and electrode pads formedinside the case including the base is omitted.

The oscillator 1 according to the first embodiment is an oven controlledcrystal oscillator (OCXO). As illustrated in FIGS. 1 and 2, theoscillator 1 includes a base 101 and a case 10 including a cap 102bonded to the base 101, and a base substrate 30 provided on the lowersurface 101 r side of the base 101. The case 10 has an accommodationspace S1 formed by the base 101 and the cap 102 provided along the outerperiphery of the base 101 and bonded to the upper surface of a flange101 b that is recessed from an upper surface 101 f of the base 101.

In the accommodation space S1 in the case 10, a plurality of pinterminals 14 that are hermetically sealed by a sealing member 103 andpenetrates the base 101, a circuit substrate 8 fixed to an end portionof the pin terminal 14 opposite to the base 101, and a resonator 2supported by the plurality of lead terminals 12 coupled to the circuitsubstrate 8 with a gap between the circuit substrate 8 and the base 101,and the circuit substrate 8. A temperature control element 7 and atemperature sensor 15 are coupled to the base 101 side of the resonator2 disposed in the accommodation space S1.

The base 101 is made of, for example, a material such as Kovar, softiron, or iron nickel, and the flange 101 b is provided on the outerperipheral portion thereof. The base 101 is provided with a plurality ofthrough-holes that penetrate from the upper surface 101 f to the lowersurface 101 r, and the conductive pin terminal 14 is inserted into eachthrough-hole. A gap between the through-hole and the pin terminal 14 ishermetically sealed by the sealing member 103 such as glass. A standoff13 made of an insulator such as glass can be provided on the lowersurface 101 r of the base 101.

The pin terminal 14 is made of a pin material such as Kovar, soft iron,or iron nickel, and has one end on the lower surface 101 r side of thebase 101, the other end on the accommodation space S1 side, and iserected along the Z-axis direction. The pin terminals 14 are constitutedwith two rows arranged along the Y-axis direction.

The cap 102 is provided with an outer peripheral portion 102 f in whicha metal thin plate such as white, kovar, soft iron, or iron-nickel isformed into a concave shape by, for example, pressing or drawing, andthe opening is bent outward in a flange shape.

Then, in the case 10, the outer peripheral portion 102 f of the cap 102is mounted on the flange 101 b of the base 101, and a portion Q wherethe flange 101 b and the outer peripheral portion 102 f overlap ishermetically sealed to form the accommodation space S1. Theaccommodation space S1 is hermetically sealed in an atmosphere ofreduced-pressure such as a pressure lower than the atmospheric pressureor an atmosphere of inert gas such as nitrogen, argon, helium.

The circuit substrate 8 can be configured by, for example, a printedsubstrate. The circuit substrate 8 has a rectangular shape in plan viewfrom the Z-axis direction, and a through-hole is provided at a positionfacing an erection position of the pin terminal 14 fixed to the base101. The circuit substrate 8 is fixed to the pin terminal 14 in a statewhere the end of the pin terminal 14 on the accommodation space S1 sideis inserted through the through-hole. The circuit substrate 8 includes alower surface 8 r that is a surface on the base 101 side, and an uppersurface 8 f that is a surface opposite to the lower surface 8 r.

On the upper surface 8 f and the lower surface 8 r of the circuitsubstrate 8, circuit patterns such as circuit wiring and terminals (notillustrated) are provided. For example, an integrated circuit element 4that oscillates the resonator 2, another electronic element 16, and thelike are coupled to the circuit pattern on the upper surface 8 f of thecircuit substrate 8.

The plurality of lead terminals 12 that support the resonator 2 arecoupled to the circuit pattern on the lower surface 8 r of the circuitsubstrate 8. The lead terminal 12 are positioned on the outer peripheralside of the circuit substrate 8 and are coupled in a coupling region R2arranged along each of the two rows to which the pin terminals 14 arecoupled. The lead terminal 12 is coupled to the resonator 2 in acoupling region R1 and supports the resonator 2.

As illustrated in FIG. 3, the resonator 2 includes a package 20 and aresonator element 3 accommodated in the package 20. The package 20includes a package base 21 on which the resonator element 3 is mounted,a lid 22 that is bonded to the package base 21 with an accommodationspace S2 provided so as to accommodate the resonator element 3 betweenthe lid 22 and the package base 21, and a frame-shaped seal ring 23positioned between the package base 21 and the lid 22 and joining thepackage base 21 and the lid 22.

The package base 21 has a cavity shape having a recess 25, and has arectangular shape whose outer shape is a substantially square shape inplan view from the Z-axis direction. However, the outer shape of thepackage base 21 is not limited to the substantially square shape, butmay be another rectangular shape.

The resonator element 3 is fixed to an internal terminal (notillustrated) provided at a step portion of the package base 21 via aconductive fixing member 29 such as a conductive adhesive, for example,at an outer edge portion thereof. A quartz crystal substrate 31constituting the resonator element 3 is obtained by making an SC cutquartz crystal substrate into a substantially circular plan view shapeby machining or the like. By using the SC cut quartz crystal substrate,it is possible to obtain the resonator element 3 in which frequency jumpand resistance increase due to spurious vibrations are small andtemperature characteristic are stable. The plan view shape of the quartzcrystal substrate 31 is not limited to a circle, and may be a non-linearshape such as an ellipse or an oval, or a linear shape such as atriangle or a rectangle.

The resonator element 3 is not limited to the SC cut quartz crystalresonator, and for example, an AT cut or BT cut quartz crystalresonator, a surface acoustic wave (SAW) resonator, or the like can beused. As the resonator element 3, for example, a piezoelectric resonatorother than the quartz crystal resonator, a micro electro mechanicalsystems (MEMS) resonator, or the like can be used. As the substratematerial of the resonator element 3, quartz crystal, piezoelectricsingle crystals such as lithium tantalate and lithium niobate,piezoelectric materials such as piezoelectric ceramics such as leadzirconate titanate, or silicon semiconductor materials can be used. Asan excitation unit of the resonator element 3, one using a piezoelectriceffect may be used, or electrostatic drive using a Coulomb force may beused.

The lid 22 has a plate shape, and is bonded to an end surface of thepackage base 21 via the seal ring 23 so as to close an opening of therecess 25. The seal ring 23 is disposed arranged in a frame shape and ispositioned between the end surface of the package base 21 and the lid22. The seal ring 23 is made of a metal material, and the package base21 and the lid 22 are hermetically bonded by melting the seal ring 23.As described above, the opening of the recess 25 is closed by the lid 22to form the accommodation space S2, and the resonator element 3 can beaccommodated in the accommodation space S2.

The accommodation space S2 of the hermetically sealed package 20 is in areduced pressure state of about 10 Pa or less, for example. With thisconfiguration, stable drive of the resonator element 3 can be continued.However, the atmosphere of the accommodation space S2 is notparticularly limited, and may be filled with inert gas such as nitrogenor argon to be at atmospheric pressure.

The constituent material of the package base 21 is not particularlylimited. For example, various ceramics such as aluminum oxide can beused. In this case, the package base 21 can be manufactured by firing alaminate of ceramic sheets. The constituent material of the lid 22 isnot particularly limited, but may be a member whose linear expansioncoefficient approximates that of the constituent material of the packagebase 21. For example, when the constituent material of the package base21 is ceramic as described above, the constituent material of the lid 22may be a metal material.

On a lower surface 21 r of the package base 21, for example, a pluralityof first coupling terminals 24 and a plurality of second couplingterminals 26 which are electrically conducted with the resonator element3 by internal wirings (not illustrated) are provided. Specifically, asillustrated in FIG. 4, four first coupling terminals 24 are arrangedalong the outer edge, and four second coupling terminals 26 are arrangedalong the outer edge on the opposite side. The number of each of thefirst coupling terminal 24 and the second coupling terminal 26 is notlimited and may be any number. The first coupling terminal 24 and thesecond coupling terminal 26 can be formed by a method in which a metalwiring material such as tungsten (W) or molybdenum (Mo) isscreen-printed and fired on the lower surface 21 r of the package base21 and nickel (Ni), gold (Au), or the like is plated thereon and thelike. Hereinafter, the lower surface 21 r of the package base 21 may bereferred to as the lower surface 21 r of the resonator 2.

In each of the first coupling terminal 24 and the second couplingterminal 26 provided on the lower surface 21 r of the resonator 2, asecond coupling portion 12 a of the lead terminal 12 is fixed byelectrical coupling using, for example, a conductive adhesive orsoldering. The resonator 2 is supported in a so-called suspended stateon the circuit substrate 8 via the lead terminal 12 by fixing a firstcoupling portion 12 d of the lead terminal 12 to be electrically coupledto the lower surface 8 r of the circuit substrate 8.

Each lead terminal 12 includes the second coupling portion 12 a providedat a position including one end, the first coupling portion 12 dprovided at a position including the other end, and a first extendingportion 12 b and a second extending portion 12 c that are positionedbetween the second coupling portion 12 a and the first coupling portion12 d and coupled by a second bent portion B2. The second couplingportion 12 a and the first extending portion 12 b are coupled by a firstbent portion B1, and the first coupling portion 12 d and the secondextending portion 12 c are coupled by a third bent portion B3. In otherwords, the lead terminal 12 includes three bent portions of the firstbent portion B1, the second bent portion B2, and the third bent portionB3 between the second coupling portion 12 a coupled to the resonator 2and the first coupling portion 12 d.

As described above, three bent portions of the first bent portion B1,the second bent portion B2, and the third bent portion B3 are providedon the lead terminal 12 between the second coupling portion 12 a coupledto the resonator 2 and the first coupling portion 12 d coupled to thecircuit substrate 8 and the resonator 2 is supported in a so-calledsuspended state with respect to the circuit substrate 8, so that thelead terminal 12 can be easily bent. Since the lead terminal 12 isconfigured to bulge at the second bent portion B2 in the outer directionof the resonator 2, rigidity of the lead terminal 12 can be furtherreduced, and impact transmitted from the circuit substrate 8 to theresonator 2 can be absorbed more effectively.

Although the lead terminal 12 is described as having a configuration inwhich four lead terminals 12 are disposed on the first coupling terminal24 side of the resonator 2 and four lead terminals 12 are disposed onthe second coupling terminal 26 side, the number of the lead terminals12 is not limited, and may be any number as long as the resonator 2 canbe supported.

The temperature control element 7 is an electronic component that iscoupled to the lower surface 21 r of the resonator 2 and controls thetemperature of the resonator 2. In the first embodiment, the temperaturecontrol element 7 is a heating element such as a power transistor, andheats the resonator 2 to keep the temperature of the resonator element 3of the resonator 2 substantially constant. By keeping the temperature ofthe resonator element 3 substantially constant, excellent frequencystability can be maintained.

The temperature sensor 15 is disposed near the resonator 2 and detectsthe temperature of the resonator 2. Particularly in the firstembodiment, the temperature sensor 15 is disposed so as to be in contactwith the outer surface of the resonator 2. As the temperature sensor 15,for example, a thermistor or a platinum resistor can be used.

The base substrate 30 can be configured by, for example, a printedcircuit substrate. The base substrate 30 includes an upper surface 30 fpositioned on the base 101 side and a lower surface 30 r that is asurface opposite to the upper surface 30 f. The base substrate 30 isprovided with a bottomed hole 34 in the upper surface 30 f facing theerection position of the pin terminal 14 fixed to the base 101. One endof the pin terminal 14 is inserted into the bottomed hole 34 of the basesubstrate 30, and the base substrate 30 is coupled to the pin terminal14 by a bonding material 33 such as soldering. A plurality of externalcoupling terminals 32 are provided on the lower surface 30 r of the basesubstrate 30.

1-1-2. Functional Configuration of Oscillator

FIG. 5 is a functional block diagram of the oscillator 1 of the firstembodiment. As illustrated in FIG. 5, the oscillator 1 of the firstembodiment includes the resonator 2 and an oscillation circuit 5. Theoscillation circuit 5 includes the integrated circuit element 4, thetemperature control element 7, and the temperature sensor 15.

The temperature control element 7 is an element that controls thetemperature of the resonator 2 based on a temperature control signalVHC, and is a heating element such as a power transistor in the firstembodiment. Heat generated by the temperature control element 7 iscontrolled according to the temperature control signal VHC supplied fromthe integrated circuit element 4. Heat generated by the temperaturecontrol element 7 is transmitted to the resonator 2, and the temperatureof the resonator 2 is controlled so as to approach a target temperature.

The temperature sensor 15 is a first temperature sensing element thatdetects a temperature and outputs a first temperature detection signalVT1 having a voltage level corresponding to the detected temperature. Asdescribed above, the temperature sensor 15 is disposed near theresonator 2 and detects the temperature around the resonator 2. Thefirst temperature detection signal VT1 output from the temperaturesensor 15 is supplied to the integrated circuit element 4. Thetemperature sensor 15 may be, for example, a thermistor or a platinumresistor.

The integrated circuit element 4 includes a digital signal processingcircuit 210, a temperature control signal generation circuit 220, acircuit for oscillation 230, a fractional N-phase locked loop (PLL)circuit 231, a frequency dividing circuit 232, an output buffer 233, anda temperature sensor 241, a selector 242, an analog/digital conversioncircuit 243, an interface circuit 250, a storage unit 260, and aregulator 270.

The circuit for oscillation 230 is a circuit which is electricallycoupled to both ends of the resonator 2, and amplifies an output signalof the resonator 2 and feeds the output signal back to the resonator 2to oscillate the resonator 2 and outputs an oscillation signal. Forexample, the circuit for oscillation 230 may be a circuit foroscillation using an inverter as an amplifying element, or may be acircuit for oscillation using a bipolar transistor as an amplifyingelement.

The fractional N-PLL circuit 231 converts a frequency of the oscillationsignal output from the circuit for oscillation 230 into a frequencycorresponding to a frequency division ratio indicated by a delta-sigmamodulated frequency division ratio control signal DIVC.

The frequency dividing circuit 232 divides the oscillation signal outputfrom the fractional N-PLL circuit 231.

The output buffer 233 buffers the oscillation signal output from thefrequency dividing circuit 232 and outputs the oscillation signal as anoscillation signal CKO to the outside of the integrated circuit element4. This oscillation signal CKO becomes an output signal of theoscillator 1.

The temperature sensor 241 is a second temperature sensing element thatdetects the temperature and outputs a second temperature detectionsignal VT2 having a voltage level corresponding to the detectedtemperature. For example, the temperature sensor 241 can be realized bya diode or the like. As described above, the integrated circuit element4 is bonded to the upper surface 8 f of the circuit substrate 8, and thetemperature sensor 241 is provided at a position farther from theresonator 2 and the temperature control element 7 than the temperaturesensor 15. Therefore, the temperature sensor 241 detects the temperatureat a position away from the resonator 2 and the temperature controlelement 7. Accordingly, when the outside air temperature of theoscillator 1 changes within a predetermined range, the temperaturedetected by the temperature sensor 15 provided in the vicinity of thetemperature control element 7 hardly changes, whereas the temperaturedetected by the temperature sensor 241 changes within a predeterminedrange. As such, the temperature sensor 241 is a temperature sensor forcapturing changes in the outside air temperature, and the temperaturesensor 241 may detect a wide temperature range when the outside airtemperature changes within a predetermined range. Therefore, in thefirst embodiment, as illustrated in FIG. 1, the integrated circuitelement 4 including the temperature sensor 241 is provided at a positionclose to the cap 102 that touches the outside air.

The selector 242 selects and outputs any one of the second temperaturedetection signal VT2 output from the temperature sensor 241 and thefirst temperature detection signal VT1 output from the temperaturesensor 15. In the first embodiment, the selector 242 selects and outputsthe second temperature detection signal VT2, and the first temperaturedetection signal VT1 in a time-sharing manner.

The analog/digital conversion circuit 243 converts the secondtemperature detection signal VT2 and the first temperature detectionsignal VT1, which are analog signals output from the selector 242 in atime-sharing manner, to a second temperature code DT2 and a firsttemperature code DT1, which are digital signals, respectively. Theanalog/digital conversion circuit 243 may convert the second temperaturedetection signal VT2 and the first temperature detection signal VT1 intothe second temperature code DT2 and the first temperature code DT1 afterconverting the voltage level of the second temperature detection signalVT2 and the first temperature detection signal VT1 by voltage divisionby a resistor or the like.

The digital signal processing circuit 210 generates a temperaturecontrol code DHC for controlling the temperature control element 7 basedon the first temperature code DT1 and the second temperature code DT2.The digital signal processing circuit 210 may generate the temperaturecontrol code DHC based on target temperature information of theresonator 2. The target temperature information of the resonator 2 isstored in a read only memory (ROM) 261 of the storage unit 260. When thepower of the oscillator 1 is turned on, the target temperatureinformation is transferred from the ROM 261 to a predetermined registerincluded in a register group 262 and held therein, and the targettemperature information held in the register is supplied to the digitalsignal processing circuit 210.

The digital signal processing circuit 210 generates the frequencydivision ratio control signal DIVC for temperature compensating afrequency of the oscillation signal based on a set value of the targetfrequency stored in the storage unit 260 and the second temperature codeDT2 D. As described above, the frequency division ratio control signalDIVC is supplied to the fractional N-PLL circuit 231, and the frequencyof the oscillation signal output from the circuit for oscillation 230 isconverted by the fractional N-PLL circuit 231 into a frequency accordingto a frequency division ratio indicated by the frequency division ratiocontrol signal DIVC. With this configuration, the frequency of theoscillation signal that slightly changes depending on the outside airtemperature is temperature compensated, and the oscillation signaloutput from the fractional N-PLL circuit 231 has a substantiallyconstant target frequency regardless of the outside air temperature.

The digital signal processing circuit 210 may include a digital filterthat performs low pass processing on at least a part of the secondtemperature code DT2 and the first temperature code DT1 output from theanalog/digital conversion circuit 243 in a time-sharing manner andreduces an intensity of a high frequency noise signal.

The temperature control signal generation circuit 220 generates andoutputs a temperature control signal VHC based on the temperaturecontrol code DHC generated by the digital signal processing circuit 210.The temperature control signal VHC is supplied to the temperaturecontrol element 7, and the amount of heat generated by the temperaturecontrol element 7 is controlled in accordance with the temperaturecontrol signal VHC. With this configuration, the temperature of theresonator 2 is controlled to be substantially constant at the targettemperature.

The interface circuit 250 is a circuit for performing data communicationwith an external device (not illustrated) coupled to the oscillator 1.The interface circuit 250 may be, for example, an interface circuitcompatible with an inter-integrated circuit (I²C)) bus or an interfacecircuit compatible with a serial peripheral interface (SPI) bus.

The storage unit 260 includes the ROM 261 that is a nonvolatile memoryand the register group 262 that is a volatile memory. In the inspectionprocess when the oscillator 1 is manufactured, the external devicewrites various data for controlling an operation of each circuitincluded in the oscillator 1 to the various registers included in theregister group 262 via the interface circuit 250 and adjusts eachcircuit. Then, the external device stores various determined optimumdata in the ROM 261 via the interface circuit 250. When the oscillator 1is turned on, the various data stored in the ROM 261 is transferred tovarious registers included in the register group 262 and held therein,and the various data held in the various registers is supplied to eachcircuit.

The regulator 270 generates a power supply voltage and a referencevoltage of each circuit included in the integrated circuit element 4based on a power supply voltage VDD supplied from the outside of theoscillator 1.

1-1-3. Temperature Control by Digital Signal Processing Circuit

Assume an oscillator of a comparative example in which the digitalsignal processing circuit 210 generates the temperature control code DHCbased on the first temperature code DT1 without using the secondtemperature code DT2. In the oscillator of the comparative example,although the temperature of the resonator 2 is controlled to besubstantially constant at the target temperature by the temperaturecontrol signal VHC, a temperature gradient of the accommodation space S1changes according to the temperature of outside air of the oscillator 1and an error occurs in the control by the temperature control signalVHC, and thus the temperature of the resonator 2 slightly changes. Incontrast, since the integrated circuit element 4 is provided at aposition away from the temperature control element close to the cap 102that touches the outside air, the temperature is likely to changeaccording to the outside air temperature.

FIG. 6 is a graph illustrating an example of a relationship between theoutside air temperature, the temperature of the resonator 2, and thetemperature of the integrated circuit element 4 in an oven controlledcrystal oscillator of the comparative example. In FIG. 6, the horizontalaxis represents the outside air temperature, and the vertical axisrepresents the temperature of the resonator 2 or the integrated circuitelement 4. The solid line indicates the temperature of the resonator 2and the one-dot chain line indicates the temperature of the integratedcircuit element 4. In the example of FIG. 6, when the outside airtemperature increases from the lower limit temperature Tmin of a rangeTR in which the operation of the oscillator 1 is guaranteed to the upperlimit temperature Tmax, the temperature of the resonator 2 decreases byΔT1. Therefore, when the outside air temperature changes, thetemperature of the resonator 2 also slightly changes, and the frequencyof the oscillation signal also slightly changes due to the temperaturecharacteristic of the resonator 2.

In the example of FIG. 6, when the outside air temperature increasesfrom the lower limit temperature Tmin to the upper limit temperatureTmax, the temperature of the integrated circuit element 4 increases byΔT2. The temperature increase ΔT2 of the integrated circuit element 4 isconsiderably larger than the temperature decrease ΔT1 of the resonator2. That is, the temperature detected by the temperature sensor 241included in the integrated circuit element 4 changes in a relativelywide range with respect to the change in the outside air temperature.Accordingly, it is possible to estimate the outside air temperature fromthe second temperature detection signal VT2 output from the temperaturesensor 241, estimate the temperature of the resonator 2 from theestimated outside air temperature, and control the temperature of theresonator 2 to be kept constant at the target temperature. Therefore, inthe oscillator 1 of the first embodiment, the digital signal processingcircuit 210 generates the temperature control code DHC based on thetarget temperature information stored in the storage unit 260 and thesecond temperature code DT2 obtained by converting the secondtemperature detection signal VT2 to control the temperature of theresonator 2 to be kept constant at the target temperature.

Specifically, the digital signal processing circuit 210 generates afirst correction code based on the second temperature code DT2, andgenerates the temperature control code DHC based on a code obtained byadding the first correction code to the first temperature code DT1. Thedigital signal processing circuit 210 performs a control operation basedon the first temperature code DT1 and the second temperature code DT2,and generates the temperature control code DHC based on a code obtainedby the control operation.

FIG. 7 is a diagram illustrating an example of generation processing ofthe temperature control code DHC by the digital signal processingcircuit 210 in the first embodiment. In the example of FIG. 7, thedigital signal processing circuit 210 performs a temperature correctionoperation for generating a first correction code DTC1 using a firstpolynomial expressed by the following expression (1), which uses thesecond temperature code DT2 as a variable. Specifically, the digitalsignal processing circuit 210 generates the first correction code DTC1by substituting the second temperature code DT2 into the followingexpression (1) In the expression (1), temperature correctioncoefficients a_(n) to a₀ are stored in the storage unit 260. The n is aninteger of 1 or more, and n may be 3 or more, that is, the firstpolynomial may be a high-order expression in order to correct the firsttemperature code DT1 with high accuracy.

DTC1=a _(n) ·DT2^(n) +a _(n-1) ·DT2^(n-1) + . . . +a ₁ ·DT2+a ₀  (1)

In the example of FIG. 7, the digital signal processing circuit 210performs the control operation including a proportional operation and anintegral operation on a temperature code DT1X obtained by adding thefirst correction code DTC1 to the first temperature code DT1.Specifically, the digital signal processing circuit 210 performs, as thecontrol operation, the proportional operation that multiplies thetemperature code DT1X by a proportional term gain coefficient and theintegration operation that integrates the temperature code DT1Xmultiplied by an integral term gain coefficient. The digital signalprocessing circuit 210 adds the code obtained by the proportionaloperation and the code obtained by the integral operation and normalizesa code obtained by the addition by multiplying the code by anormalization gain coefficient, as the control operation. Theproportional term gain coefficient, the integral term gain coefficient,and the normalization gain coefficient are stored in the storage unit260 as target temperature information, for example.

The digital signal processing circuit 210 can correct an error withrespect to a target value of the code obtained by the proportionaloperation by adding the code obtained by the integral operation to thecode obtained by the proportional operation.

In the example of FIG. 7, the digital signal processing circuit 210performs the control operation in a floating-point format, and convertsa code obtained by the control operation into a code of fixed-pointformat. Furthermore, the digital signal processing circuit 210 generatesthe temperature control code DHC by performing delta-sigma modulation onthe code of fixed-point format obtained based on the control operation.

Specifically, the digital signal processing circuit 210 integrates thecode of fixed-point format obtained based on the control operation at arate faster than an update rate of the first temperature code DT1, andoutputs a carry bit of the integrated code as the temperature controlcode DHC. That is, the digital signal processing circuit 210 outputs, asthe temperature control code DHC, the most significant bit that is acarry bit of an (n+1)-bit code obtained by integrating the n-bit code offixed-point format.

In the example of FIG. 7, the temperature control signal generationcircuit 220 includes an analog filter 221 to which the temperaturecontrol code DHC is input, and the temperature control element 7 iscontrolled based on the temperature control signal VHC output from theanalog filter 221. The analog filter 221 may be, for example, a low-passfilter or a band-pass filter. FIG. 8 is a graph illustrating an exampleof waveforms of the temperature control code DHC and the temperaturecontrol signal VHC. In FIG. 8, the horizontal axis represents time, andthe vertical axis represents voltage. In the example of FIG. 8, the1-bit temperature control code DHC is a pulse density modulated code,and the temperature control signal VHC output from the analog filter 221is a sine wave signal obtained by demodulating the temperature controlcode DHC.

By controlling the temperature control element 7 with the temperaturecontrol signal VHC generated in this way, the temperature of theresonator 2 is kept constant at the target temperature, and theoscillation signal CKO with high frequency accuracy is obtained.

1-1-4. Effect

As described above, in the oscillator 1 according to the firstembodiment, in the integrated circuit element 4 included in theoscillation circuit 5, the analog/digital conversion circuit 243converts the first temperature detection signal VT1 output from thetemperature sensor 15 and the second temperature detection signal VT2output from the temperature sensor 241 into the first temperature codeDT1 and the second temperature code DT2, respectively. The digitalsignal processing circuit 210 generates the temperature control code DHCfor controlling the temperature of the temperature control element 7based on the first temperature code DT1 and the second temperature codeDT2. Specifically, the digital signal processing circuit 210 generatesthe first correction code DTC1 by the first polynomial expressed by theexpression (1) using the second temperature code DT2 as a variable, andgenerates the temperature control code DHC based on the temperature codeDT1X obtained by adding the first correction code DTC1 to the firsttemperature code DT1. Then, the temperature control signal generationcircuit 220 generates and outputs the temperature control signal VHCbased on the temperature control code DHC generated by the digitalsignal processing circuit 210. Accordingly, according to the oscillator1 of the first embodiment, even if the temperature of the resonator 2fluctuates due to fluctuation in the outside air temperature, the firsttemperature code DT1 is corrected based on the second temperature codeDT2 that changes due to fluctuation in the outside air temperature andthe temperature of the resonator 2 can be kept constant at the targettemperature, and thus it is possible to reduce the possibility that thefrequency accuracy is lowered due to the fluctuation in the outside airtemperature.

In the oscillator 1 of the first embodiment, the digital signalprocessing circuit 210 performs the control operation including theproportional operation and the integration operation based on the firsttemperature code DT1 and the second temperature code DT2, and generatesthe temperature control code DHC based on the code obtained by thecontrol operation. Accordingly, according to the oscillator 1 of thefirst embodiment, the error with respect to the target value of the codeobtained by the proportional operation is corrected by the code obtainedby the integral operation, and thus it is possible to control thetemperature control element 7 with high accuracy by the temperaturecontrol code DHC, and it is possible to further reduce the possibilitythat the frequency accuracy is lowered due to the fluctuation in theoutside air temperature.

In the oscillator 1 of the first embodiment, the digital signalprocessing circuit 210 generates the temperature control code DHC byperforming delta-sigma modulation on the code of fixed-point formatobtained based on the control operation. Specifically, the digitalsignal processing circuit 210 integrates the code of fixed-point formatobtained based on the control operation at a rate faster than the updaterate of the first temperature code DT1, and outputs the carry bit of theintegrated code as the temperature control code DHC. Due to a noiseshaping effect of delta-sigma modulation at the rate faster than theupdate rate of the first temperature code DT1, the noise included in thetemperature control code DHC is distributed over a wide band, and thenoise in a band of the temperature control signal VHC is reduced.Accordingly, according to the oscillator 1 of the first embodiment, itis possible to control the temperature control element 7 with highaccuracy, and it is possible to further reduce the possibility that thefrequency accuracy is lowered due to the fluctuation in the outside airtemperature.

In the oscillator 1 of the first embodiment, the temperature controlsignal generation circuit 220 includes the analog filter 221 to whichthe temperature control code DHC is input, and the temperature controlelement 7 is controlled based on the temperature control signal VHCoutput from the analog filter 221. Accordingly, according to theoscillator 1 of the first embodiment, since a multi-bit digital/analogconversion circuit is not required for converting the temperaturecontrol code DHC into the temperature control signal VHC, the size ofthe integrated circuit element 4 can be reduced.

According to the oscillator 1 of the first embodiment, the digitalsignal processing circuit 210 can also be used as an computing unit suchas an adder or a multiplier by performing processing for generating thetemperature control code DHC in a time-sharing manner with otherprocessing, and thus it is possible to reduce the size of the integratedcircuit element 4 as compared with the case where the temperaturecontrol element 7 is controlled by an analog circuit.

Also, according to the first embodiment, since various coefficientvalues used for operation by the digital signal processing circuit 210are stored in the storage unit 260, the coefficient values can be set tooptimum values according to the characteristic of the individualoscillators 1, and the oscillator 1 with high frequency accuracy can berealized.

1-2. Second Embodiment

In the oscillator 1 of the first embodiment, when the power supplyvoltage VDD fluctuates, the amount of heat generated by the integratedcircuit element 4 changes, and thus the temperature of the integratedcircuit element 4 changes. Furthermore, when the amount of heatgenerated by the integrated circuit element 4 changes, the temperaturegradient of the accommodation space S1 changes and the temperature ofthe resonator 2 also changes slightly.

FIG. 9 is a graph illustrating an example of a relationship between thepower supply voltage VDD and the temperature of the integrated circuitelement 4. FIG. 10 is a graph illustrating an example of a relationshipbetween the power supply voltage VDD and the temperature of theresonator 2. FIGS. 9 and 10 illustrate the temperatures of theintegrated circuit element 4 and the resonator 2, respectively, when thepower supply voltage VDD is increased from 3.0 V to 3.6 V by 0.1 V everyabout 8 minutes when the outside air temperature is +25° C.,respectively. In FIGS. 9 and 10, the solid line indicates thetemperature of the integrated circuit element 4 or the resonator 2, andthe broken line indicates the power supply voltage VDD. As illustratedin FIG. 9, when the power supply voltage VDD increases from 3.0 V to 3.6V, the temperature of the integrated circuit element 4 increases byabout 1.5° C. and the amount of heat generated by the integrated circuitelement 4 increases, and as a result, the temperature of the resonator 2also increases by about 0.12° C. as illustrated in FIG. 10.

As described above, the temperature of the resonator 2 changes dependingon the magnitude of the power supply voltage VDD, and the frequency ofthe oscillation signal fluctuates depending on the temperaturecharacteristic of the resonator 2. Therefore, in the oscillator 1 of thesecond embodiment, the digital signal processing circuit 210 generatesthe temperature control code DHC based on a power supply voltage codeDVD converted from the power supply voltage VDD, so that the temperatureof the resonator 2 can be controlled to be constant at the targetfrequency even if the power supply voltage VDD fluctuates.

Hereinafter, for the oscillator 1 of the second embodiment, the sameconfigurations as those in the first embodiment are denoted by the samereference numerals, descriptions similar to those in the firstembodiment are omitted or simplified, and contents different from thosein the first embodiment will be mainly described.

FIG. 11 is a functional block diagram of the oscillator 1 of the secondembodiment. As illustrated in FIG. 11, in the oscillator 1 of the secondembodiment, in the integrated circuit element 4, the selector 242selects and outputs one of the power supply voltage VDD supplied to theoscillator 1, the second temperature detection signal VT2 output fromthe temperature sensor 241, and the first temperature detection signalVT1 output from the temperature sensor 15 in a time-sharing manner.

The analog/digital conversion circuit 243 converts the power supplyvoltage VDD, the second temperature detection signal VT2, and the firsttemperature detection signal VT1, which are output from the selector 242in a time-sharing manner, to the power supply voltage code DVD, thesecond temperature code DT2, and the first temperature code DT1, whichare digital signals, respectively. The analog/digital conversion circuit243 may convert the voltage level of the power supply voltage VDD, thesecond temperature detection signal VT2, and the first temperaturedetection signal VT1 into the power supply voltage code DVD, the secondtemperature code DT2, and the first temperature code DT1 afterconverting the voltage level of the power supply voltage VDD, the secondtemperature detection signal VT2, and the first temperature detectionsignal VT1 by voltage division by a resistor or the like.

The digital signal processing circuit 210 generates the temperaturecontrol code DHC for controlling the temperature of the temperaturecontrol element 7 based on the first temperature code DT1, the secondtemperature code DT2, and the power supply voltage code DVD.Specifically, the digital signal processing circuit 210 generates thefirst correction code based on the second temperature code DT2, andgenerates the temperature control code DHC based on the code obtained byadding the first correction code to the first temperature code DT1. Thedigital signal processing circuit 210 generates the second correctioncode based on the power supply voltage code DVD, and generates thetemperature control code DHC based on the code obtained by adding thesecond correction code to the first temperature code DT1.

The digital signal processing circuit 210 may include the digital filterthat performs low pass processing on at least a part of the power supplyvoltage code DVD, the second temperature code DT2 and the firsttemperature code DT1 output from the analog/digital conversion circuit243 in a time-sharing manner and reduces an intensity of a highfrequency noise signal.

FIG. 12 is a diagram illustrating an example of generation processing ofthe temperature control code DHC by the digital signal processingcircuit 210 in the second embodiment. In the example of FIG. 12, thedigital signal processing circuit 210 performs a temperature correctionoperation for generating the first correction code DTC1 by using thefirst polynomial expressed by the expression (1) described above usingthe second temperature code DT2 as a variable. Specifically, the digitalsignal processing circuit 210 generates the first correction code DTC1by substituting the second temperature code DT2 into the expression (1)described above.

In the example of FIG. 12, the digital signal processing circuit 210performs a power supply voltage correction operation for generating asecond correction code DTC2 by using a second polynomial expressed bythe following expression (2), which uses the power supply voltage codeDVD as a variable. Specifically, the digital signal processing circuit210 generates the second correction code DTC2 by substituting the powersupply voltage code DVD into the second polynomial expressed by thefollowing expression (2). In the expression (2), power supply voltagecorrection coefficients b_(m) to b₀ are stored in the storage unit 260.The m is an integer of 1 or more, and m may be 3 or more, that is, thesecond polynomial may be a high-order expression in order to correct thesecond temperature code DT2 that fluctuates according to the magnitudeof the power supply voltage VDD with high accuracy.

DTC2=b _(m) ·DVD ^(m) +b _(m-1) ·DVD ^(m-1) + . . . +b ₁ ·DVD+b ₀  (2)

In the example of FIG. 12, the digital signal processing circuit 210performs the same control operation as the first embodiment on thetemperature code DT1X obtained by adding the first correction code DTC1and the second correction code DTC2 to the first temperature code DT1.

Similarly to the first embodiment, the digital signal processing circuit210 converts the code obtained by the control operation into a code offixed-point format, and generates the temperature control code DHC byperforming delta-sigma modulation on the code. The temperature controlcode DHC is input to the analog filter 221 included in the temperaturecontrol signal generation circuit 220, and the signal output from theanalog filter 221 is supplied to the temperature control element 7 asthe temperature control signal VHC.

By controlling the temperature control element 7 with the temperaturecontrol signal VHC generated in this way, the temperature of theresonator 2 is kept constant at the target temperature, and theoscillation signal CKO with high frequency accuracy is obtained.

Other configurations of the oscillator 1 of the second embodiment arethe same as those of the oscillator 1 of the first embodiment, and thusdescription thereof is omitted.

As described above, in the oscillator 1 of the second embodiment, in theintegrated circuit element 4 included in the oscillation circuit 5, theanalog/digital conversion circuit 243 converts first temperaturedetection signal VT1 output from the temperature sensor 15, the secondtemperature detection signal VT2 output from the temperature sensor 241,and the power supply voltage VDD into the first temperature code DT1,the second temperature code DT2, and the power supply voltage code DVD,respectively. The digital signal processing circuit 210 generates thetemperature control code DHC for controlling the temperature of thetemperature control element 7 based on the first temperature code DT1,the second temperature code DT2, and the power supply voltage code DVD.Specifically, the digital signal processing circuit 210 generates thefirst correction code DTC1 by the first polynomial expressed by theexpression (1) using the second temperature code DT2 as a variable,generates the second correction code DTC2 by the second polynomialexpressed by the expression (2) using the second temperature code DT2 asa variable, and generates the temperature control code DHC based on thetemperature code DT1X obtained by adding the first correction code DTC1and the second correction code DTC2 to the first temperature code DT1.Then, the temperature control signal generation circuit 220 generatesand outputs the temperature control signal VHC based on the temperaturecontrol code DHC generated by the digital signal processing circuit 210.Accordingly, according to the oscillator 1 of the second embodiment,even if the temperature of the resonator 2 fluctuates due to thefluctuation in the outside air temperature or the power supply voltageVDD fluctuates, the first temperature code DT1 can be corrected based onthe second temperature code DT2 and the power supply voltage code DVDand the temperature of the resonator 2 can be kept constant at thetarget temperature, and thus it is possible to reduce the possibilitythat the frequency accuracy is lowered due to the fluctuations in theoutside air temperature and power supply voltage.

According to the oscillator 1 of the second embodiment, the firsttemperature code DT1 can be corrected with higher accuracy by making thesecond polynomial expressed by the expression (2) a higher orderexpression. That is, according to the oscillator 1 of the secondembodiment, it is possible to reduce the possibility that the frequencyaccuracy is lowered due to the fluctuation in the power supply voltageVDD by generating the second correction code DTC2, by the digital signalprocessing circuit 210, based on the high order expression of the thirdor higher order using the power supply voltage code DVD as a variable.

In the oscillator 1 of the second embodiment, the digital signalprocessing circuit 210 performs the control operation including theproportional operation and integral operation based on the firsttemperature code DT1, the second temperature code DT2, and the powersupply voltage code DVD and generates the temperature control code DHCbased on the code obtained by the control operation. Accordingly,according to the oscillator 1 of the second embodiment, the error withrespect to the target value of the code obtained by the proportionaloperation is corrected by the code obtained by the integral operation,and thus it is possible to control the temperature control element 7with high accuracy by the temperature control code DHC, and it ispossible to further reduce the possibility that the frequency accuracyis lowered due to the fluctuations in the outside air temperature andthe power supply voltage.

In addition, according to the oscillator 1 of the second embodiment, thesame effects as those of the oscillator 1 of the first embodiment can beobtained.

1-3. Modification Example

In each of the embodiments described above, the temperature controlelement 7 and the temperature sensor 15 are provided as separate bodies,but may be included in one integrated circuit element, and theintegrated circuit element may be disposed near the resonator 2. In thiscase, for example, the temperature control element 7 can be realized bya resistor and a MOS transistor, and the temperature sensor 15 can berealized by a diode or the like.

In each of the embodiments described above, the integrated circuitelement 4 includes one temperature sensor 241, but may include aplurality of temperature sensors 241. In this case, for example, theanalog/digital conversion circuit 243 may convert a plurality oftemperature detection signals output from the plurality of temperaturesensors 241 into a plurality of temperature codes, and the digitalsignal processing circuit 210 may generate the second temperature codeDT2 based on the plurality of temperature codes. For example, thedigital signal processing circuit 210 may use an average value of theplurality of temperature codes as the second temperature code DT2.

In each of the embodiments described above, the temperature sensor 241is included in the integrated circuit element 4, but may be providedoutside the integrated circuit element 4 and at a position farther fromthe resonator 2 and the temperature control element 7 than thetemperature sensor 15. In this case, the temperature sensor 241 can berealized by, for example, a thermistor or a platinum resistor. FIG. 13is a cross-sectional view of the oscillator 1 illustrating an example inwhich the temperature sensor 241 is provided outside the integratedcircuit element 4. In the example of FIG. 13, the temperature sensor 241is bonded to the upper surface 8 f of the circuit substrate 8, and isprovided at a position close to the cap 102 that touches the outsideair. Accordingly, the range in which the temperature detected by thetemperature sensor 241 changes with respect to the change in the outsideair temperature is widened, and the temperature of the resonator 2 canbe kept at the target temperature with high accuracy.

In each of the embodiments described above, the control operationperformed by the digital signal processing circuit 210 includes theproportional operation and the integral operation, but may furtherinclude other operation such as a differential operation. By adding acode obtained by the differential operation to the code obtained by theproportional operation and the integral operation, overshoot and huntingwith respect to the target value can be reduced.

In each of the embodiments described above, the digital signalprocessing circuit 210 outputs the 1-bit temperature control code DHC byperforming delta-sigma modulation on the code converted into thefixed-point format and the temperature control code DHC is convertedinto the temperature control signal VHC by the analog filter 221 of thetemperature control signal generation circuit 220, but the temperaturecontrol code DHC may be supplied to the temperature control element 7 ifpossible. In this case, the temperature control signal generationcircuit 220 is not necessary. Alternatively, the digital signalprocessing circuit 210 outputs the n-bit temperature control code DHCwithout performing the delta-sigma modulation, and the temperaturecontrol signal generation circuit 220 may convert the n-bit temperaturecontrol code DHC into the temperature control signal VHC by adigital/analog conversion circuit instead of the analog filter 221.

In each of the embodiments described above, although temperaturecompensation is performed by controlling the frequency division ratio ofthe fractional N type PLL circuit based on the frequency division ratiocontrol signal DIVC generated by the digital signal processing circuit210, the temperature compensation method is not limited thereto. Forexample, the circuit for oscillation 230 may have a capacitor array, andtemperature compensation may be performed by selecting a capacitancevalue of the capacitor array based on the temperature compensation codeDCMP generated by the digital signal processing circuit 210. Forexample, the circuit for oscillation 230 may have a variable capacitanceelement for adjusting the frequency, and the D/A conversion circuit mayconvert the temperature compensation code DCMP generated by the digitalsignal processing circuit 210 into an analog signal, and temperaturecompensation may be performed by controlling the capacitance value ofthe variable capacitance element based on the signal.

In the first embodiments described above, although one analog/digitalconversion circuit 243 converts the first temperature detection signalVT1 and the second temperature detection signal VT2 into the firsttemperature code DT1 and the second temperature code DT2, respectively,in a time-sharing manner, for example, the analog/digital conversioncircuit may include a plurality of analog/digital converters and theplurality of analog/digital converters may convert the first temperaturedetection signal VT1 and the second temperature detection signal VT2into the first temperature code DT1 and the second temperature code DT2,respectively. Similarly, in the second embodiment described above,although one analog/digital conversion circuit 243 converts the powersupply voltage VDD, the first temperature detection signal VT1, and thesecond temperature detection signal VT2 into the power supply voltagecode DVD, the first temperature code DT1, and the second temperaturecode DT2, respectively, in a time-sharing manner, for example, theanalog/digital conversion circuit may include a plurality ofanalog/digital converters and the plurality of analog/digital convertersmay convert the power supply voltage VDD, the first temperaturedetection signal VT1, and the second temperature detection signal VT2into the power supply voltage code DVD, the first temperature code DT1,and the second temperature code DT2, respectively.

In each of the embodiments described above, although the temperaturecontrol element 7 is a heating element such as a power transistor, thetemperature control element 7 may be any element that can control thetemperature of the resonator 2 and may be a heat absorption element suchas a Peltier element depending on the relationship between the targettemperature of the resonator 2 and the outside air temperature.

In each of the embodiments described above, the oscillator 1 is anoscillator having a temperature control function for adjusting thetemperature of the resonator 2 to the vicinity of the target temperaturebased on the first temperature code DT1 and the second temperature codeDT2 and a temperature compensation function based on the secondtemperature code DT2, but may be an oscillator having a temperaturecontrol function and not having a temperature compensation function. Theoscillator 1 may be an oscillator having a temperature control functionand a frequency control function, such as a voltage controlled ovencontrolled crystal oscillator (VC-OCXO).

2. Electronic Apparatus

FIG. 14 is a functional block diagram illustrating an example of aconfiguration of an electronic apparatus according to the embodiment ofthe present disclosure.

An electronic apparatus 300 according to the embodiment of the presentdisclosure is configured to include an oscillator 310, a processingcircuit 320, an operation unit 330, a read only memory (ROM) 340, arandom access memory (RAM) 350, a communication unit 360, and a displayunit 370. The electronic apparatus of the embodiment of the presentdisclosure may have a configuration in which some of constitutionalelements in FIG. 14 are omitted or changed, or other constitutionalelements are added.

The oscillator 310 includes an oscillation circuit 312 and a resonator313. The oscillation circuit 312 oscillates the resonator 313 andgenerates an oscillation signal. The oscillation signal is output froman external terminal of the oscillator 310 to the processing circuit320.

The processing circuit 320 operates based on an output signal from theoscillator 310. For example, the processing circuit 320 performs variouscalculation processing and control processing using the oscillationsignal input from the oscillator 310 as a clock signal in accordancewith a program stored in the ROM 340 or the like. Specifically, theprocessing circuit 320 performs various processing according tooperation signals from the operation unit 330, processing forcontrolling the communication unit 360 to perform data communicationwith an external device, and processing for transmitting a displaysignal for displaying various types of information on the display unit370, and the like.

The operation unit 330 is an input device including operation keys,button switches, and the like, and outputs an operation signal accordingto an operation by a user to the processing circuit 320.

The ROM 340 is a storage unit that stores programs, data, and the likefor the processing circuit 320 to perform various calculation processingand control processing.

The RAM 350 is used as a work area of the processing circuit 320, and isa storage unit that temporarily stores programs and data read from theROM 340, data input from the operation unit 330, operation resultsexecuted by the processing circuit 320 according to various programs,and the like.

The communication unit 360 performs various controls for establishingdata communication between the processing circuit 320 and the externaldevice.

The display unit 370 is a display device configured by a liquid crystaldisplay (LCD) or the like, and displays various types of informationbased on the display signal input from the processing circuit 320. Thedisplay unit 370 may be provided with a touch panel that functions asthe operation unit 330.

By applying, for example, the oscillator 1 of each embodiment describedabove as the oscillator 310, it is possible to reduce the possibilitythat the frequency accuracy is lowered due to the fluctuation in theoutside air temperature, and thus a highly reliable electronic apparatuscan be realized.

Various electronic apparatuses are conceivable as such an electronicapparatus 300, and examples thereof include a personal computer such asa mobile-type computer, a laptop-type computer, a tablet-type computer,a mobile terminal such as a smartphone and a mobile phone, a digitalcamera, an ink jet ejection device such as an ink jet printer, a storagearea network device such as a router and a switch, local area networkequipment, mobile terminal base station equipment, a TV, a video camera,a video recorder, a car navigation device, a real-time clock device, apager, an electronic notebook, an electronic dictionary, a calculator,an electronic game device, a game controller, a word processor, aworkstation, a video phone, a crime prevention TV monitor, electronicbinoculars, a POS terminal, medical equipment such as an electronicthermometer, a blood pressure monitor, a blood glucose meter, anelectrocardiogram measuring device, an ultrasonic diagnostic device, anelectronic endoscope, a fish finder, various measuring instruments,instruments for a vehicle, an aircraft, a ship, and the like, a flightsimulator, a head mounted display, a motion tracing device, a motiontracking device, a motion controller, and a pedestrian dead reckoning(PDR) device.

FIG. 15 is a diagram illustrating an example of an appearance of asmartphone that is an example of the electronic apparatus 300. Asmartphone that is the electronic apparatus 300 includes a button as theoperation unit 330 and an LCD as the display unit 370. Then, thesmartphone that is the electronic apparatus 300 can reduce thepossibility that the frequency accuracy is lowered due to thefluctuation in the outside air temperature, for example, by applying theoscillator 1 of each of the embodiments described above as theoscillator 310, and thus a highly reliable electronic apparatus 300 canbe realized.

As another example of the electronic apparatus 300 of the embodiment ofthe present disclosure, a transmission apparatus that functions as aterminal base station apparatus or the like that performs communicationwith a terminal in a wired or wireless manner using the oscillator 310described above as a reference signal source may be included. As theoscillator 310, for example, by applying the oscillator 1 of each of theembodiments described above, it is also possible to realize theelectronic apparatus 300 that can be used for, for example, acommunication base station and that is desired to have high frequencyaccuracy, high performance, and high reliability at a lower cost than inthe past.

Another example of the electronic apparatus 300 according to theembodiment of the present disclosure may be a communication apparatusincluding a frequency control unit in which the communication unit 360receives an external clock signal and the processing circuit 320controls the frequency of the oscillator 310 based on the external clocksignal and an output signal of the oscillator 310. The communicationapparatus may be, for example, a backbone network device such as StratumIII or a communication device used for a femtocell.

3. Vehicle

FIG. 16 is a diagram illustrating an example of a vehicle according tothe embodiment of the present disclosure. A vehicle 400 illustrated inFIG. 16 is configured to include an oscillator 410, processing circuits420, 430, and 440, a battery 450, and a backup battery 460. The vehicleaccording to the embodiment of the present disclosure may have aconfiguration in which some of the constitutional elements in FIG. 16are omitted or other components are added.

The oscillator 410 includes an oscillation circuit and a resonator (notillustrated), and the oscillation circuit oscillates the resonator andgenerates an oscillation signal. This oscillation signal is output fromthe external terminal of the oscillator 410 to the processing circuits420, 430, and 440 and used as, for example, a clock signal.

The processing circuits 420, 430, and 440 operate based on an outputsignal from the oscillator, and perform various control processing of anengine system, a brake system, a keyless entry system, and the like.

The battery 450 supplies power to the oscillator 410 and the processingcircuits 420, 430, and 440. The backup battery 460 supplies power to theoscillator 410 and the processing circuits 420, 430, and 440 when anoutput voltage of the battery 450 falls below a threshold value.

By applying, for example, the oscillator 1 of each of embodimentdescribed above as the oscillator 410, it is possible to reduce thepossibility that the frequency accuracy is lowered due to thefluctuation in the outside air temperature, and thus a highly reliablevehicle can be realized.

As such a vehicle 400, various vehicles are conceivable, and examplesthereof may include automobiles such as electric cars, airplanes such asjets and helicopters, ships, rockets, and artificial satellites.

The present disclosure is not limited to the embodiment of the presentdisclosure, and various modification examples may be made thereto withinthe scope of the gist of the present disclosure.

The embodiments and modification example described above are merelyexamples, and the present disclosure is not limited thereto. Forexample, it is possible to appropriately combine each embodiment andeach modification example.

The present disclosure includes configurations that are substantiallythe same as the configurations described in the embodiments, forexample, configurations that have the same functions, methods, andresults, or configurations that have the same purposes and effects. Thepresent disclosure includes a configuration in which a non-essentialpart of the configuration described in the embodiment is remounted. Thepresent disclosure includes a configuration that exhibits the sameoperational effects as the configuration described in the embodiment ora configuration that can achieve the same object. The present disclosureincludes a configuration in which a known technique is added to theconfiguration described in the embodiment.

What is claimed is:
 1. An oscillator comprising: a resonator; atemperature control element that controls a temperature of theresonator; a first temperature sensing element that outputs a firsttemperature detection signal; a second temperature sensing element thatis provided at a position farther from the resonator than the firsttemperature sensing element and outputs a second temperature detectionsignal; an analog/digital conversion circuit that converts the firsttemperature detection signal into a first temperature code which is adigital signal, and converts the second temperature detection signalinto a second temperature code which is a digital signal; and a digitalsignal processing circuit that generates a temperature control code forcontrolling the temperature control element based on the firsttemperature code and the second temperature code.
 2. The oscillatoraccording to claim 1, wherein the digital signal processing circuitgenerates a first correction code based on the second temperature codeand generates the temperature control code based on a code obtained byadding the first correction code to the first temperature code.
 3. Theoscillator according to claim 1, wherein the analog/digital conversioncircuit converts a power supply voltage into a power supply voltage codewhich is a digital signal, and the digital signal processing circuitgenerates the temperature control code based on the first temperaturecode, the second temperature code, and the power supply voltage code. 4.The oscillator according to claim 3, wherein the digital signalprocessing circuit generates a second correction code based on the powersupply voltage code, and generates the temperature control code based ona code obtained by adding the second correction code to the firsttemperature code.
 5. The oscillator according to claim 4, wherein thedigital signal processing circuit generates the second correction codebased on a high-order expression of a third or higher order using thepower supply voltage code as a variable.
 6. The oscillator according toclaim 1, wherein the digital signal processing circuit performs acontrol operation based on the first temperature code and the secondtemperature code, and generates the temperature control code based on acode obtained by the control operation.
 7. The oscillator according toclaim 6, wherein the control operation includes a proportional operationand an integral operation.
 8. The oscillator according to claim 6,wherein the digital signal processing circuit generates the temperaturecontrol code by performing delta-sigma modulation on a code obtainedbased on the control operation.
 9. The oscillator according to claim 6,wherein the digital signal processing circuit integrates the codeobtained based on the control operation at a rate faster than an updaterate of the first temperature code, and outputs a carry bit of theintegrated code as the temperature control code.
 10. The oscillatoraccording to claim 8, further comprising: an analog filter to which thetemperature control code is input, wherein the temperature controlelement is controlled based on a signal output from the analog filter.11. The oscillator according to claim 1, further comprising: anintegrated circuit element that includes the digital signal processingcircuit and the second temperature sensing element.
 12. An electronicapparatus comprising: the oscillator according to claim 1; and aprocessing circuit that operates based on an output signal from theoscillator.
 13. A vehicle comprising: the oscillator according to claim1; and a processing circuit that operates based on an output signal fromthe oscillator.